Star cluster formation in cosmological simulations – III. Dynamical and chemical evolution
Star cluster formation in cosmological simulations – III. Dynamical and chemical evolution
复制标题
宇宙学模拟中的星团形成 - III。
DOI：
--
复制
发表时间：
2018
影响因子：
4.8
通讯作者：
O. Gnedin
中科院分区：
文献类型：
--
作者：
Hui Li;O. Gnedin
在本系列的前几篇论文中，我们开发了一种新的算法，用于模拟星系形成模拟中的星星团的形成。在这里，我们调查如何解散绑定星星集群影响的形状的集群质量函数和金属丰度分布的幸存集群。星团演化包括恒星的损失，由于潮汐破裂而变得不受束缚，以及由于恒星演化而造成的质量损失。我们计算了沿着星系团轨迹的潮汐张量，并用它来估计瞬时质量损失率。典型的潮汐张量在100亿年的时间尺度上表现出很大的变化，在星系团形成后的第一个Gyr中，最大特征值为10^7 $~Gyr$^{-2}$，中值为10^4 $~Gyr$^{-2}$。作为动力学破坏的结果，在我们的模拟的最终可用输出在红移$z\approx1.5$，集群质量函数有一个近似对数正态的形状，峰值为$\sim10^{4.3}M_\odot$。外推的破坏，以$z=0$的结果在太多的低质量的星系团相比，观察到的银河系球状星团（GC）。超过70%的GC候选者在现在之前被完全破坏;只有10%的GC候选者总质量留在幸存的簇中。在z=0时幸存的星系团的总质量在每次运行中的变化范围为（2-6）× 10^7 M_\odot $，这与银河系大小的星系中GC系统的观测质量一致。所有大质量星星团和幸存的GC的金属丰度分布具有相似的形状，但不同的标准化，因为集群中断。该模型产生了一个更大的分数非常贫金属的集群比观察到的。该模型的一个可靠的预测是年龄-金属丰度关系，其中富金属的星系团系统地比贫金属的星系团年轻3~Gyr。
In previous papers of this series, we developed a new algorithm for modeling the formation of star clusters in galaxy formation simulations. Here we investigate how dissolution of bound star clusters affects the shape of the cluster mass function and the metallicity distribution of surviving clusters. Cluster evolution includes the loss of stars that become unbound due to tidal disruption as well as mass-loss due to stellar evolution. We calculate the tidal tensor along cluster trajectories and use it to estimate the instantaneous mass-loss rate. The typical tidal tensor exhibits large variations on a time-scale of $\sim100$~Myr, with maximum eigenvalue of $10^7$~Gyr$^{-2}$, and median value of $10^4$~Gyr$^{-2}$ for the first Gyr after cluster formation. As a result of dynamical disruption, at the final available output of our simulations at redshift $z\approx1.5$, the cluster mass function has an approximately log-normal shape peaked at $\sim10^{4.3}M_\odot$. Extrapolation of the disruption to $z=0$ results in too many low-mass clusters compared to the observed Galactic globular clusters (GCs). Over 70\% of GC candidates are completely disrupted before the present; only 10\% of the total GC candidate mass remains in surviving clusters. The total mass of surviving clusters at $z=0$ varies from run to run in the range $(2-6)\times10^7M_\odot$, consistent with the observed mass of GC systems in Milky Way-sized galaxies. The metallicity distributions of all massive star clusters and of the surviving GCs have similar shapes but different normalization because of cluster disruption. The model produces a larger fraction of very metal-poor clusters than observed. A robust prediction of the model is the age-metallicity relation, in which metal-rich clusters are systematically younger than metal-poor clusters by up to 3~Gyr.
影响因子：
6.5
作者：
Nina Brinkmann;S. Banerjee;Bhawna Motwani;P. Kroupa
通讯作者：
Nina Brinkmann;S. Banerjee;Bhawna Motwani;P. Kroupa